The subject invention is directed toward the art of chain power drives and, more particularly, to a chain guide and tensioner apparatus useful in confined spaces for applying a tensioning force to a chain traveling therepast.
Several prior art patents show chain tensioner devices that include a chain engaging shoe member formed from a plastic material with a metal spring or bracket incorporated therein to provide the shoe with the necessary resiliency and rigidity while taking advantage of the plastics low friction and good wear characteristics. For example, my prior U.S. Pat. No. 4,921,472 discloses a chain tensioner wherein a blade spring is received in longitudinal passageways formed in a plastic shoe. The spring is retained in longitudinal position by internal shoulders in the passageways. Lateral positioning and retention is achieved by cooperation between longitudinal slots in the ends of the spring and central internal walls in the passageways.
One of the disadvantages present with my prior design, as well as other prior art designs, is that the necessary slots, holes, and the like formed in the spring for retention purposes weaken the spring and require increasing its overall dimensions to achieve the tensioning force required. Additionally, the manufacturing cost of the springs can increase significantly because of added processing steps needed to form the slots and openings. Likewise, the molding of the plastic shoe can require somewhat complex molds because of the internal retaining walls and tabs.
The above discussed factors can result in a chain tensioner that is somewhat more complex and expensive than is desirable.